Sen. Evan Bayh had already collected the 4,500 ballot-petition signatures needed to run in this year’s Indiana Democratic primary, and his last-minute decision not to run leaves the Indiana Democratic Party in the position of having to select its candidate itself. There probably isn’t a realistic way for anyone to gather the signatures needed by this week’s deadline.

A Democratic source told TPMDC that Bayh’s campaign did polling last week and found the senator was ahead of Republican Dan Coats, a candidate who just jumped in the race. Bayh had completed all the petitions for the race, which are due this week, the source said.

R.J. Gerard, communications director for the Indiana Democratic Party confirmed to TPMDC that the state Democratic Party would be able to select a new candidate to run in November’s general election if no one files petitions with 4,500 signatures (500 within each of the state’s nine House districts) to run in the primary.

The petitions must be filed with the county clerk’s office by Tuesday. Then candidates have until Friday to file with the Secretary of State for the primary ballot. The lack of another Democrat will mean there is a vacancy, leaving it to the state party’s State Central Committee to choose a candidate at its June 30 meeting.“I would imagine that it would be the plan, depending on what happens between now and Friday,” Gerard said. Gerard did not know whether any discussions are going on with potential new candidates.

This means the Indiana Democrats would avoid holding a primary to choose who will be their nominee in the fall.

The Democratic source speculated Bayh’s choice seems like a personal decision that must have come at the last minute given all the legwork that had been done.

Bayh talked to President Obama this morning about his decision not to seek reelection, a source close to Obama told TPMDC.

The source says Obama and Bayh have had “several conversations” about 2010 and the senator made his personal decision this weekend.

“It is personal not at all political – he is by nature a Governor not a Senator,” the source said.

The source added that Bayh had been interested in something else at the end of this term since 2006 and noted Bayh’s strong financial standing with $13 million in the bank and 20-point lead in the polls.